For ambulatory electrocardiogram recorders, such instruments are nowadays characterized by a case worn or carried by the patient, e.g., on a belt or in a pocket, and connected to some number of electrodes or other external sensors. The recorder is controlled by a microcontroller, and the data that it senses, either raw or after preprocessing, is typically stored on a large-capacity removable data medium so as to enable data to be recorded in full over a very long period, typically in the range one day to several months.
Nowadays, magnetic recording media (cassettes) have been replaced by electronic memories such as flash memories, which are both rewritable and non-volatile, and which are now available with relatively very large memory capacities.
The recorder then comprises a case provided on one side with an opening through which the removable memory card can be inserted. Once the recording has been completed, the card containing the data that has been sensed is extracted from the case and is handed over to the practitioner or is sent to a remote center for analyzing the data contained therein for diagnostic purposes.
The use of a reprogrammable microcontroller presents the advantage of enabling the instrument to be upgraded without requiring any component changes, nor even changes of the instrument as a whole. Reprogramming the microcontroller can be used to correct possible defects in the program and/or to add new functions to existing instruments by means of new versions of the program, thus making it possible to satisfy clients who are very sensitive to progress.
In general, reprogramming the microcontroller requires a specific connection to be made to the microcontroller, as defined by the manufacturer of the component, and usually comprising a serial link and a plurality of associated control lines. The printed circuit carrying the microcontroller carries some number of contacts for reprogramming purposes, and these must be accessible from the outside without dismantling the instrument, e.g., via an opening formed in the case in register with the reprogramming contacts, which opening must be capable of being closed off permanently except while reprogramming is taking place by means of a suitable closure member.
Since the recorder is carried by the patient under a wide variety of circumstances and over a long duration, it can be subjected to an environment that is wet, dusty, etc., and it is essential to protect the removable memory and the circuit inside the case effectively therefrom. The environment in which the instrument is to be found can also present disturbances in the form of parasitic electrical fields and the risk of electrostatic discharges. Access to the card connector, and also to any other opening in the case (in particular the opening giving access to the reprogramming contacts), thereby needs to be protected against this type of attack from the outside environment.
In order to perform reprogramming, the opening giving access to the reprogramming contacts is uncovered so as to give access to these various contacts. These contacts then have signals applied thereto serving to force the microcontroller to take on a reprogramming mode, and then various special combinations of signals are applied to the control lines in a predetermined sequence enabling the microcontroller to be controlled in desired manner.
These specific connections require a relatively large number of contacts and control lines leading to the microcontroller, and that complicates the design of the instrument, which it is desired to make as small as possible with as few as possible external openings in order to better satisfy the general requirements of portable instruments.